Memory devices are typically provided as internal, semiconductor, integrated circuit devices in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and flash memory.
Flash memory devices have developed into a popular source of non-volatile memory for a wide range of electronic applications. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Changes in threshold voltage (Vt) of the memory cells, through programming (which is often referred to as writing) of charge storage structures (e.g., floating gates or charge traps) or other physical phenomena (e.g., phase change or polarization), determine the data value of each cell. Common uses for flash memory include personal computers, tablet computers, digital cameras, digital media players, cellular telephones, solid state drives and removable memory modules, and the uses are growing.
One type of flash memory cell is a single level cell (SLC) which may be programmed to a targeted one of two different data states, such as 1 or 0. Another type of flash memory cell is a multi-level cell (MLC) which may be programmed to a targeted one of more than two data states. MLCs may provide higher density memories without increasing the number of memory cells since each cell might represent more than one bit.
A data state of a flash memory cell might be determined by sensing the stored charge on the charge storage structure (i.e., Vt) of the memory cell. Charge storage in charge storage structures of neighboring memory cells may inadvertently change the functional Vt of the selected memory cell, particularly if several neighboring memory cells are in a programmed state. When combined with other factors, such as capacitive coupling, temperature fluctuations, program/erase cycling, and storage of multiple bits of data per memory, the influence of neighboring charge storage structures may cause a memory cell to be misread.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative methods of operating memory, and apparatus to perform such methods.